This invention relates to power transmission fluid compositions which exhibit reduced static friction coefficients.
This invention is based on the discovery that reaction products of certain maleic or succinic acids and/or anhydrides and primary C4-C30 amines are effective in reducing the static friction levels of such fluids.
Reduction of friction in mechanical devices is one critical aspect of improving their energy efficiency. Reducing friction reduces the amount of energy that is turned into heat which in most devices is radiated to the environment and thereby the energy is lost. Therefore there is a continuing interest in developing chemical compositions that reduce sliding contact friction. In power transmission fluids there is a need not only to lower friction, usually the static friction, but to control that level of friction accurately. An additional aspect of friction control is the maintenance of the desired level friction, that is, once a desirable level of friction is achieved that the established level not vary with aging of the fluid.
For the purposes of this invention a power transmission fluid is defined as any lubricant used in contact with gears involved in the transmission of mechanical energy. In many cases these devices also contain wet clutch systems employing friction materials based on cellulose, polyamides (KEVLAR®), carbon fibers or other composite materials. Commonly these power transmission devices, which may use the fluids of this invention, would include, but not be limited to, automatic transmissions, manual transmissions, continuously variable transmissions, automated manual transmissions, dual clutch manual transmissions, transfer cases, axles and differentials used in mobile applications. They would also include stationary gearing used in industrial applications as well as industrial transmissions.